Once upon a time a little girl opened a book and discovered a glorious place: of fauns and kings and dwarves and talking badgers and lots of delicious hot sausages and sticky Turkish Delight and a lion-god who romped with children across heathery downs. After turning the last page of "The Lion, the Witch, and the Wardrobe," she would never be the same. She had entered a portal that led to Narnia, the enchanting realm conjured by C.S. Lewis, and had emerged with her imagination somehow transfigured. From then on, the joy of "The Chronicles of Narnia," all seven books, became the measure by which she judged everything she read. And when she realized, somewhere around early adolescence, that the realm of Narnia did not exist -- had never existed -- it felt like a knife in her heart.

Does my story sound familiar? Millions of young readers have been caught in Narnia's spell since the books were published in the 1950s, most probably believing, in the solipsistic way of children, that their fierce love of Narnia was peculiar to them. As Laura Miller learned when she set about writing "The Magician's Book: A Skeptic's Adventures in Narnia," the yearning to breathe Narnian air, so intense and personal in childhood, turns out to be utterly commonplace.

So too, it appears, is the eventual adult detection of the Christian underpinnings of C.S. Lewis's novels for children. For some, gaining the understanding that the lion-god Aslan is a stand-in for Jesus has come as a weird relief. It confirmed the quasi-religious stirrings we felt when we encountered the books the first time.

Others, such as Ms. Miller, have been outraged by what seems a betrayal, the smuggling-in of an agenda: "Of course, the self-sacrifice of Aslan to compensate for the treachery of Edmund was exactly like the crucifixion of Christ to pay off the sins of mankind! How could I have missed that?" she writes of the realization. "I felt angry and humiliated because I had been fooled."

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C.S. Lewis (1898-1963) at Oxford University in 1950.
Getty Images

The revelation of Lewis's religious message put Ms. Miller off Narnia for years. A non-Christian, she still cannot warm to this aspect of the stories. Yet "The Magician's Book" constitutes a return of sorts. It recounts Ms. Miller's thoughtful and humane journey back to an appreciation of what Lewis created. But it is more than a personal story: It is also an exploration of Lewis's life, his intellectual inclinations and his literary friendships, as well as an extended meditation on the "soul-shaping potential" of reading itself.

C.S. Lewis embarked on "The Chronicles of Narnia" after observing to his friend and fellow Oxford don J.R.R. Tolkien that "there is too little of what we really like in stories. I am afraid we shall have to try to write some ourselves." What both men liked was called by Lewis "Northernness," with all the thunder-gods and Valkyries that the term might suggest. Each writer was enthralled by the power of myth, by "story's deep roots in the human mind," as Ms. Miller puts it. "Lewis felt that certain important truths could be fully communicated only via stories," she tells us. "What was captured, or was meant to be captured, was ineffable."

Egged on by Lewis, Tolkien would eventually write "The Lord of the Rings," a vast fantasy so complete that it included entire languages. Tolkien was a fanatic for narrative consistency and deeply invested in the internal coherence of his imaginary Middle-earth. It is a world that to the elf-averse, Ms. Miller remarks, "looks like nothing more than the biggest model-railroad setup of all time."

Narnia, by contrast, is a jumble of classical and Northern mythology, pagan imagery, medieval themes (and clothes), Christian allegory and fairy tales, into which tumbles a succession of postwar British schoolchildren, some of whom, thrillingly, become kings and queens. "Lewis's magpie aesthetic made Narnia a grab bag of every motif that had ever captured his fancy," Ms. Miller observes.

‘What remains is a dim recollection of how life was shaped before I knew about Narnia, and a more distinct sense of what it was like afterward. I had found a new world, which at the same time felt like a place I'd always known existed.’

For young enthusiasts, Lewis's joyful syncretism makes the books if anything even more exciting: The abundance of allusions creates a sense that Narnia is really reachable through our own world. As a child I didn't know the Norse origins of the wolf Fenris Ulf, but I knew about centaurs and felt comforted when suddenly Father Christmas turned up in the snowy landscape of "The Lion, the Witch, and the Wardrobe" to hand out mugs of steaming hot drinks.

This incongruous Yuletide cameo particularly irritated Tolkien, who confessed after Lewis's death that the Narnia books were "outside the range of my sympathy." In fact, he detested them. Tolkien was not -- is not -- alone in deprecating "The Chronicles of Narnia." Lewis's most famous modern critic (one might even say enemy) is the atheist novelist Philip Pullman, who has called the Narnia books "repellent" and "morally loathsome."

Already alienated by Lewis's Christian themes, Laura Miller also found herself, as an adult, wrestling with his snobbery, sexism and racial prejudice. These evils abound in her least favorite of the Narnia series, "The Horse and His Boy," which includes Lewis telling how "dark men came round [the Narnians] in a thick crowd, smelling of garlic and onions, their white eyes flashing dreadfully in their brown faces."

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Ms. Miller doesn't give Lewis a complete pass for expressing such retrograde chauvinism, but it's a continually refreshing characteristic of "The Magician's Book" that she comes down, again and again, on the side of imaginative liberality. "Myths and stories are repositories of human desires and fears, which means that they contain our sexual anxieties, our preoccupation with status, and our xenophobia as well as our heroism, our generosity, and our curiosity," she writes. "If we were to purge our shelves of all the great books tainted by one vile idea or another, we'd have nothing left to read -- or at least nothing but the new and blandly virtuous."

Ms. Miller is especially sympathetic to an idea of Lewis's that was regarded at the time as offbeat -- and still is. He argued that a book could be judged by how it is read. "A hater of progress, newfanglement, and vulgarity," Ms. Miller writes, "Lewis was not a notably tolerant man, but reading brought out the populist in him." Lewis thought that the esteem of readers "might be the best way to appreciate a book's worth, especially since he regarded the literary mandarins of his day as slaves to pernicious intellectual fads."

And indeed, for Ms. Miller -- for a lot of us -- the seven volumes of "The Chronicles of Narnia" did more than open a door to one particular fictional place: They were the books that made readers of us. Her discovery of Narnia, Ms. Miller writes, "showed me how I could tumble through a hole in the world I knew and into another, better one, a world fresher, more brightly colored, more exhilarating, more fully felt than my own."

And those aspects of Narnia that so grated for Tolkien -- its hodgepodge of myths and themes -- actually provide a clue to the mesmerizing nature of the books. "Narnia is the country of literature, of books, and of reading, a territory so vast that it might as well be infinite," Ms. Miller concludes, ending her long estrangement from the books that had given her such joy in childhood. "At nine I thought I must get to Narnia or die. It would be a long time before I understood that I was already there."

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